A torque-controlled humanoid robot riding on a two-wheeled mobile platform

This paper is motivated by the questions: What would happen if a humanoid robot is put on a Segway? Is it possible for the humanoid robot to use this transportation device that is specifically designed for human? Simulation involving a two-wheeled mobile platform (TWMP) and our humanoid robot COMAN (COmpliant HuMANoid Platform) shows that it is indeed feasible without any hardware modification. Regarding the implementation, the full dynamics of the humanoid robot is considered and quadratic optimization is employed to generate whole-body joint torques to realise two types of tasks according to the interaction type between the TWMP and the humanoid robot. The TWMP is considered as unknown disturbance and the humanoid robot has to keep balancing on it in the first type of task. On the contrary, the active movement of the humanoid robot is utilised as an interface to intuitively drive the TWMP in the second type of task. For both tasks, tracking the position of center of mass (CoM) and regulating the angular momentum around it are considered as primary objectives, stabilizing the posture of certain part of its body is optional. In addition, both tasks are repeated on uneven terrain to demonstrate the robustness of the control method.